Maybe they need to diversify ....... add a little more colour ........so to speak
Canadian bills are made of polycarbonate plastic rather than paper, and are multicolored rather than all being greenish. They wear much better and you can even wash them if you want. They have a transparent window and a laser holograph to prevent counterfeiting. They also have raised dots so blind people can read them. They cost a bit more than American bills, but they last several times as long.
Canada has also dropped $1 and $2 bills because $1 and $2 coins last about 20 times as long as bills.
American bills are made of plain old paper and have no windows or holographs, and it is difficult for normal people to distinguish them in low light, never mind blind people
So boring.